Trailer Vehicle Coupling Safety Aids

ABSTRACT

A system for monitoring the coupling of a tractor to a trailer of an articulated road vehicle, the tractor mounting a hitch assembly ( 7 ) for coupling to a king pin ( 9 ) downwardly depending from the underside of the trailer ( 10 ), comprises a sensor ( 14 ) producing an electrical signal proportional to the vertical distance between the hitch assembly and the underside of the trailer, and indicator means ( 16 ) connected to the sensor for providing an indication of the vertical distance.

FIELD OF THE INVENTION

This invention relates to an articulated vehicle trailer couplingposition detector and locking detector.

BACKGROUND OF THE INVENTION

Conventionally, the tractor and trailer of an articulated road vehicleare coupled together through a “fifth-wheel” arrangement in which a kingpin extending downwardly from the underside of the trailer is engagedwith and locked into a coupling on the tractor. The coupling typicallyincludes a hitch plate having an opening or throat in its rearward endto guide the king pin into the coupling socket at the centre as thetractor is reversed into position beneath the parked trailer. Once theking pin is in position in the coupling socket, it is lockedautomatically as the mechanism closes around it. The driver normallychecks this has happened by engaging 1^(st) gear and pulling against thetrailer, as the trailer brakes have not been released by the air line atthis stage the vehicle should not move.

The coupling operation requires some precision, firstly to ensure thatthe king pin enters the throat centrally and at the right height, andsecondly to ensure that the king pin is engaged and locked into thecoupling socket. If the king pin is too high relative to the hitchplate, it is possible for it to miss the socket entirely and to land infront of the hitch plate when the trailers temporary supporting legs areraised. This can give the impression to the operator that the trailer iscorrectly coupled when it is not. When the tractor is driven forwards,the trailer follows, but as soon as the vehicle seeks to negotiate acorner, the trailer can become detached, with damaging and potentiallydangerous consequences.

Even if the king pin is correctly located in the coupling socket,failure of the locking mechanism to operate correctly can lead todetachment of the trailer from the tractor in use Again, theconsequences of this will be at least substantial damage to the trailer,and may lead to a road traffic accident involving other vehicles.

It is therefore highly desirable to ensure that the coupling of thetractor to the trailer is carried out correctly on every occasion.

EP-A-1 295 783 discloses a system for monitoring the fifth wheel hitchon a tractor and trailer combination. Three sensors are provided on ornear the fifth wheel assembly on the tractor. A first sensor detectsrotation of the hitch plate about a horizontal axis as the king pinmoves over it, a second sensor detects the presence of the king pin endin the socket, while a third sensor detects the locking mechanism whenit is in the locked position. This arrangement is clearly advantageousover the conventional arrangements in providing confirmation of thecorrect positioning of the king pin, it still requires the tractordriver to position the tractor accurately with respect to the trailer.If, for example, the hitch plate is too low relative to the king pin orthe alignment of the tractor relative to the longitudinal axis of thetrailer is incorrect, the driver is given no indication of this.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a system for monitoring thecoupling of a tractor to a trailer of an articulated road vehicle, thetractor mounting a hitch assembly for coupling to a king pin downwardlydepending from the underside of the trailer, the system comprising asensor producing an electrical signal proportional to the verticaldistance between the hitch assembly and the underside of the trailer,and indicator means connected to the sensor for providing an indicationof the vertical distance.

In one configuration, the system comprises a pair of sensors mounted onthe tractor and laterally spaced one from the other relative to thedirection of travel of the vehicle. The sensors are preferably locatedto the rear of the hitch assembly on the tractor, one on each side ofthe centre-line of the tractor. Additional sensors are provided on thetractor outwardly and rearwardly of the first sensors.

In an alternative configuration, the system has first and second sensorsmounted on the centre line of the tractor, the first located at therearmost part of the tractor, in order to give the earliest possibledetection of passage underneath the trailer, and the second just infront of the hitch assembly. In this way, a warning can be provided whenthe rear end of the tractor first moves beneath the front end of thetrailer, and a further warning can be provided when the hitch assemblyreaches the desired position beneath the trailer.

The indicator means preferably include a controller arranged to comparethe respective signals and to output signals to an indicator devicemounted in the tractor adjacent to the driver thereof to provide visualand/or audible indications when either of the following conditionsapplies:

a) the said vertical distance is not within a predetermined range; or

b) the difference between the vertical distances detected by the twosensors is greater than a predetermined value.

The or each sensor preferably comprises an ultrasonic transmitterarranged to transmit acoustic energy upwardly and an associatedultrasonic detector to detect the energy reflected back from a surfaceabove the sensor. By determining the time taken for the ultrasound totravel to the surface and back, a measurement of the distance can beobtained. Ultrasonic sensors are preferred because they are lessaffected than optical devices by the build-up of dust and dirt in thearea of the fifth wheel. The transmitter and receiver may be integratedinto a single unit, or they may be separate devices spaced one from theother.

The ultrasonic sensors may transmit brief pulses of acoustic energy,with sufficient time between adjacent pulses to allow for detection ofthe reflected signal. Alternatively, the sensors may transmit continuouswave energy modulated with a code or pattern whose reflection can bediscriminated in the received signal, thereby permitting the time offlight of the signal between the sensor and the underside of the trailerto be determined, and thus the distance. Since speed will depend onfactors such as temperature and atmospheric pressure, it may benecessary to incorporate into the system at least one temperature sensorand/or atmospheric pressure sensor, and to program the control means toapply a correction factor according to the temperature and/or pressuredetected.

Other forms of sensor may be used where the conditions permit, forexample based on the reflection of radio waves. In a very simplearrangement, the sensors comprise hinged vertical probes which, whencontacted by the underside of the trailer, are deflected. The deflectioncan be measured in a number of different ways, for example by apotentiometer attached to the hinge or pivot point for each probe. Animage sensor or camera could be used in conjunction with an imagerecognition system to identify and located the king pin, for example. Itwould be possible for such a system to determine height relative to thetractor by, for example, assessing the image size of the king pin end.Alternatively, a pair of cameras could be used, deducing height from therelative image positions of the king pin end. Calibration markings couldbe provided underneath the trailer to assist in distance and positionassessment.

Conveniently, the sensors are located on the chassis of the tractor, forexample adjacent to, but below, either side of the entrance to thethroat in the hitch plate. In this way, trailers having a relativelynarrow width in the region of the king pin, for example fluid tankers,can be detected accurately. A correctly aligned king pin will passbetween the sensors and not be detected by them. Sideways misalignmentwill result in one sensor detecting the end of the king pin, by virtueof its relative proximity to the sensor compared with the remainder ofthe underside of the trailer.

Additional sensors of the same general type may be provided at each sideof the tractor vehicle to provide indications of the presence or absenceof the trailer body above the additional sensors, thereby providing anearlier indication of misalignment of the tractor and trailer,especially where the trailer is a substantially flat-bottomedconstruction, for example a box-trailer. This will also permit detectionof significant sideways error resulting in the king pin missing theentrance to the throat, and hence the throat sensors, altogether.

A further sensor may be located within or beneath the coupling socket todetect the presence of the king pin in the socket.

The system may include means for detecting the locked position of thehitch lock. This may simply comprise a proximity detector adjacent to amoving component of the locking mechanism such that proximity is onlyindicated when the mechanism is fully locked. Alternatively, thedetector may be located in the mechanism so as to indicate the unlockedstate thereof.

The system may be arranged to provide a visible and/or audibleindication externally of the tractor as well as inside the tractor,especially in relation to the correct location and locking of the kingpin in the hitch, so that others can be alerted of an error.

The audible indication, whether inside or outside the tractor, mayconsist of a pre-recorded or digitally-synthesised voice message, forexample “TRAILER UNLOCKED”. Other audible indications may be used toguide the driver without his having to look at a visual display, forexample to indicate misalignment.

In further embodiments, the system can be arranged to control thesuspension height of the tractor automatically in response to thedistance measurements detected, to ensure correct positioning. Thecoupling lock indicator signal may be used to actuate a solenoid in theparking brake air line for the trailer, closing the line and preventingthe brakes from being released when the hitch lock is not correctlyapplied.

In one embodiment of the invention, at least one additional sensor isprovided to measure the height of the tractor chassis above the ground.This may give an absolute measurement or a relative measurement. Forexample, a downward-facing ultrasonic sensor may be mounted on thetractor chassis. This could be focused on the ground or on a suspensioncomponent, such as an axle, which has a fixed relationship with theground (although this would, of course, be dependent to some extent ontyre compression).

The advantage of measuring vehicle chassis height is that, with aconfiguration as described hereinbefore, when the tractor vehicle'ssuspension is raised so that the fifth wheel assembly on the tractorapproaches the trailers rubbing plate, the sensor in front of thefifth-wheel measures a decreasing distance. After contact is made,further raising of the tractor suspension lifts the trailer, causing themeasured distance in front of the fifth-wheel to start increasing again.By using the ground distance measurement, confirmation could be obtainedthat the tractor height is still increasing. This is desirable, becausethe same effect of increasing height measured in front of thefifth-wheel could also be given by lowering again after the moment ofcontact. Although it might be possible to achieve a similar effect bymonitoring the changes in height detected by the sensor to the rear ofthe fifth-wheel assembly at the same time, generally the underside ofthe trailer at this location is less regular, and errors can thereforebe introduced. While it might be possible to filter these out, theprovision of ground measurement provides a simpler solution, and alsoaffords the possibility of monitoring the overall vehicle height, forexample.

In yet another embodiment of the invention, a sensor fixed to the backof the tractor cab could be configured to measure the horizontaldistance between the rear of the cab and the front of the trailer. Thiscould be useful in providing a warning for the driver if the distance istoo small, giving rise to a risk of the trailer corners hitting the rearof the cab during turns. The exact minimum distance at which this riskarises depends on the position of the fifth-wheel (in some tractorvehicles the fifth-wheel assembly is adjustable in a fore-and-aftdirection), and the distance of the king pin from the front of thetrailer. It would be possible to configure the system of the inventionto calculate these distances. This could be done by detecting the kingpin as it passes over the rear sensor and at the same time recording themeasurement of cab-to-trailer distance from the horizontal sensor on thecab rear. As the distance from the cab to the rear sensor is known, thedistance of the king pin from the front of the trailer can bedetermined. When the king pin locks into the fifth-wheel, thecab-to-trailer distance can be added to the trailer front to king pinmeasurement to ascertain the actual position of the fifth-wheel pivot.Assuming a normal box type trailer, the corner clearance can then bemeasured and an alarm given if this is below predetermined limits.

Another aspect of the invention provides a system for monitoring thecoupling of a tractor to a trailer of an articulated road vehicle, thetractor having a hitch lock associated with the hitch assembly and thetrailer having landing legs which are raised to permit towing of thetrailer and lowered to support the trailer when the tractor is uncoupledtherefrom, the system comprising detector means for detecting the lockedposition of the hitch lock, locking means for preventing raising of thelanding legs, and control means for receiving a signal from the detectormeans to indicate locking of the hitch lock and for releasing thelanding leg locking means only in response to receipt of said signal.

Yet another aspect of the invention provides a system for monitoring thecoupling of a tractor to a trailer of an articulated road vehicle, thetractor having a hitch lock associated with the hitch assembly and thetrailer having parking brakes releasable by air pressure in a controlline from the tractor to the trailer, the system comprising detectormeans for detecting the locked position of the hitch lock, a solenoidvalve in the compressed air supply from the tractor to the trailerparking brakes, and control means for receiving a signal from thedetector means to indicate locking of the hitch lock and for opening thesolenoid valve only in response to receipt of said signal.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which illustrate an exemplary embodiment of theinvention:

FIG. 1 is a diagrammatic top plan view of a tractor incorporating asystem according to the invention;

FIG. 2 is an enlarged diagrammatic partial side elevation of the tractorof FIG. 1; and

FIG. 3 is a view corresponding to that of FIG. 1, showing an alterativearrangement.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

The drawings illustrate diagrammatically a typical articulated tractorand trailer unit, FIG. 1 showing the tractor and FIG. 2 showing a partof the tractor and a part of the trailer. The tractor is of conventionalform and consists of a cab 1 at least partially located over the engineand transmission and front wheels, not shown. The tractor chassis hastwo main support beams 2 extending longitudinally and mounting the rearwheels 3. Enclosed wheel arches 4 are mounted over the wheels to containspray and dirt. These are carried by mounting arms 5 extending from thebeams 2.

The fifth wheel assembly comprises a mounting frame 6 attached to thebeams 2 and carrying a hitch plate 7 pivotally mounted thereon by meansof a transversely-extending pivot 8 so that the plate 7 can present aninclined surface to facilitate engagement of the king pin 9 on theunderside of the trailer 10, as hereinafter described. The plate 7 hastapering slot 11 therein to guide the king pin laterally into a couplingsocket 12 provided with a lock in conventional manner (not shown) tolock the king pin in position. The locking mechanism is unlocked by arelease arm 13 extending out to one side of the fifth wheel assembly.

A first pair of ultrasonic sensors 14 is positioned on the chassisbehind and below the hitch plate 7, one on each side of the centre-lineof the tractor to flank the entrance to the tapering slot 11 in thehitch plate 7. The sensors 14 are configured to direct a narrow beam ofacoustic energy vertically upwardly, detecting any of the ultrasoundreflected back from a surface above, that is to say, the underside 10 ofthe trailer. The sensors 14 are connected to a controller 15 in the cabof the tractor, which is programmed to detect whether the underside ofthe trailer is detected by each of the sensors within a predeterminedrange above it. The controller 15 then provides signals to an indicatordisplay device 16 adjacent to the driver within the cab to indicate, forexample by means of suitable warning lights and/or sounds, that thetrailer is within range and is over or under the desired distance abovethe tractor chassis, and also whether the alignment between the tractorand the trailer is correct; the absence of a signal on one side onlyindicates misalignment. A further indication can be given by detectionof an abnormally small height from one of the sensors, showing that theking pin 9 is passing over the sensor.

A second pair of sensors 17 is positioned outwardly and rearwardly ofthe first sensors 14, one on each of the wheel arches 4 to give anadditional, earlier, indication of misalignment of the tractor with thetrailer, especially in the case of a flat-bed or box trailer. The secondsensors 17 are also ultrasonic sensors directed upwardly, and areconfigured to detect the underside of the trailer at its lateralextremities before the king pin approaches the fifth wheel assembly. Ifone sensor 17 detects the underside of the trailer within an acceptableheight range, while the other does not, the driver is given amisalignment indication on the display 16.

For correct detection of curved trailer bodies such as fluid tankerbodies, it may be possible to direct the second sensors 17 inwardly atan oblique angle to the vertical so that a reflected signal can bedetected from the curved sides.

FIG. 3 illustrates a system with an alternative configuration ofsensors, A first ultrasonic sensor 30 of the type described withreference to FIG. 1 is located on the centre line of the tractorvehicle, on the rearmost part of the chassis of the vehicle, and isdirected vertically upwards. A second ultrasonic sensor 31, also on thecentre line of the tractor, is mounted just in front of the hitch plate7, and if the hitch plate assembly is slidable, it will be linked to itto slide with it. Each sensor is connected to the controller 15, asdescribed hereinbefore.

In use, the system is also linked to the reversing light circuit of thetractor so that, when reverse gear is engaged prior to reversing thetractor to couple the trailer, the system can issue a warning to thedriver, if no trailer is connected, to lower the suspension on thetractor in preparation for coupling the trailer. This can be done by avoice message, which also instructs the driver to reverse slowly until awarning beep is heard. The first sensor 30 detects the front of theunderside of the trailer as it passes underneath, and this signal causesthe system to emit an audible tone (“beep”) as a position indicator, andpossibly a voice message telling the driver to stop at this point if thetractor suspension is detected to be too high relative to the trailer,so that the driver has an opportunity to lower the suspension further.In either case, a voice message will then tell the driver to reverseslowly until the next warning beep, and then stop.

The passage of the front edge of the trailer over the second sensor 31generates a signal causing the system to produce an audible beep and avoice message telling the driver to stop and then raise the suspension.When the correct height is achieved, the system tells the driver to stopraising the suspension. The hitch plate or fifth wheel assembly 7 is nowin contact with the rubbing plate 10 (FIG. 2) on the underside of thetrailer, and the system then issues a voice instruction to the driver toreverse slowly until the king-pin locks in the fifth-wheel/hitch plate.The system monitors the lock status of the fifth-wheel as hereinafterdescribed, and then informs the driver when a proper lock has beenachieved and the vehicle is ready to drive forward.

The tractor may be provided with a rearwardly-directed ultrasonic sensor32 on the rear of the cab to detect and measure the front of the trailerbody, and a downwardly-directed sensor 33 at the rearmost part of thevehicle chassis to measure the vehicle chassis height above the groundin order to provide the indication of the lifting and lowering of thetractor suspension during the procedure described above. While thissensor is shown in FIG. 3 as a separately-mounted component, in practiceit may be convenient to mount this in the same housing as the sensor 30.

The hitch lock may be provided with a suitable detector to provide asignal indicating whether or not the lock is engaged. The detector maybe linked into the controller 15 to provide an indication on the display16, and may additionally or alternatively be linked to a separatewarning light 18 and/or buzzer on the outside of the cab or on thechassis, visible/audible to anyone positioned to the side of the vehicleto give a warning that the vehicle is about to be moved without thehitch lock being correctly engaged.

The hitch lock detector can also be connected electrically to a solenoidvalve in the air line (not shown) connected between the tractor and thetrailer to permit release of the trailer parking or spring brakes. Thesebrakes are configured to be held on, preventing movement of the trailer,until air pressure is applied from the tractor to release them. Thesystem may be configured to hold the solenoid valve closed until thehitch lock detector signals full engagement of the lock.

Additionally, or alternatively, an electrically-operated lock may beprovided on the trailer landing legs, preventing them from being lifteduntil the hitch lock engagement signal has been received by thecontroller 15.

The hitch lock detector may be a micro switch engaged by a movingcomponent of the lock, or a proximity detector, for example a magneticproximity detector, adjacent to the engaged position of a component ofthe lock.

Additional sensors may be positioned within the slot 11 to giveinformation about the position of the king pin relative thereto toassist in correct location of the pin in the coupling socket. A sensormay be located within or beneath the socket to give further confirmationof correct positioning.

In order to give confirmation of the situation where the king pinapproaches the fifth wheel at the correct height, but laterallydisplaced from it, sensors may be mounted on the sides of the hitchplate directing a beam of ultrasound horizontally and laterally of thetractor.

1. A system for monitoring the coupling of a tractor to a trailer of anarticulated road vehicle, the tractor mounting a hitch assembly forcoupling to a king pin downwardly depending from the underside of thetrailer, the system comprising a sensor producing an electrical signalproportional to the vertical distance between the hitch assembly and theunderside of the trailer, and indicator means connected to the sensorfor providing an indication of the vertical distance.
 2. A systemaccording to claim 1, comprising a pair of the sensors mounted on thetractor and laterally spaced one from the other relative to thedirection of travel of the vehicle.
 3. A system according to claim 2,wherein the sensors are located to the rear of the hitch assembly on thetractor, one on each side of the centre-line of the tractor.
 4. A systemaccording to claim 1, comprising first and second sensors mounted on thecentre line of the tractor, the first located at the rearmost part ofthe tractor, and the second just in front of the hitch assembly.
 5. Asystem according to claim 1, comprising an upwardly-directed sensor ateach side of the tractor vehicle to detect the presence or absence ofthe trailer thereabove, thereby indicating correct or incorrectalignment of the trailer and tractor.
 6. A system according to claim 2,wherein the indicator means include a controller arranged to compare therespective signals and to output signals to an indicator device mountedin the tractor adjacent to the driver thereof to provide visual and/oraudible indications when one of the following conditions applies: a) thesaid vertical distance is not within a predetermined range; and b) thedifference between the vertical distances detected by the two sensors isgreater than a predetermined value.
 7. A system according to claim 6,wherein the controller is arranged to provide voice messages and/orvisual indications to guide a driver of the tractor vehicle duringcoupling of the trailer to the tractor, in response to said signals. 8.A system according to claim 1, wherein the tractor comprisesvariable-height suspension, and the system also comprises adownwardly-directed sensor mounted on the tractor to measure thedistance from the ground.
 9. A system according to claim 1, wherein thetractor has a cab mounting on the rear face thereof a horizontally andrearwardly directed sensor to measure the distance from the front faceof the trailer.
 10. A system according to claim 1, wherein the or eachsensor comprises an ultrasonic transmitter arranged to transmit acousticenergy upwardly and an associated ultrasonic receiver to detect theenergy reflected back from a surface above the sensor.
 11. (canceled)12. A system according to claim 10, wherein the transmitter and receiverare separate devices spaced one from the other.
 13. A system accordingto claim 10, wherein the transmitters are arranged to transmit briefpulses of acoustic energy, the time interval between adjacent pulsesbeing sufficient for the associated receiver to detect the reflectedenergy.
 14. A system according to claim 1, wherein a further sensor islocated within or beneath the coupling socket to detect the presence ofthe king pin therein.
 15. A system according to claim 1, wherein thetractor has a hitch lock associated with the hitch assembly, and thesystem comprises means for detecting the locked position of the hitchlock.
 16. A system according to claim 15, wherein the means fordetecting the locked position of the hitch lock comprises a proximitydetector positioned adjacent to a movable component of the hitch lock.17. A system according to claim 15, wherein the control means is linkedto a solenoid valve in the compressed air supply from the tractor to thetrailer parking brakes, and is arranged to hold the valve closed,thereby preventing release of the trailer parking brakes, until themeans for detecting the locked position of the hitch lock signals thatthe hitch lock is locked.
 18. A system according to claim 1, comprisingadditional visible and/or audible warning means outside the tractorvehicle and connected to the control means for indicating the unlockedstate of the hitch lock mechanism.
 19. A system according to claim 1,wherein the control means is linked to the tractor suspension control tocontrol the height of the tractor hitch assembly relative to the trailerautomatically in response to the distance detected by the sensors.
 20. Asystem for monitoring the coupling of a tractor to a trailer of anarticulated road vehicle, the tractor having a hitch lock associatedwith the hitch assembly and the trailer having landing legs which areraised to permit towing of the trailer and lowered to support thetrailer when the tractor is uncoupled therefrom, the system comprisingdetector means for detecting the locked position of the hitch lock,locking means for preventing raising of the landing legs, and controlmeans for receiving a signal from the detector means to indicate lockingof the hitch lock and for releasing the landing leg locking means onlyin response to receipt of said signal.
 21. A system for monitoring thecoupling of a tractor to a trailer of an articulated road vehicle, thetractor having a hitch lock associated with the hitch assembly and thetrailer having parking brakes releasable by air pressure in a controlline from the tractor to the trailer, the system comprising detectormeans for detecting the locked position of the hitch lock, a solenoidvalve in the compressed air supply from the tractor to the trailerparking brakes, and control means for receiving a signal from thedetector means to indicate locking of the hitch lock and for opening thesolenoid valve only in response to receipt of said signal.